Dual Role of Organic Matter As Electron Shuttle and Sequestrator Governs the Persistence of Triclosan.

Triclosan (TCS), one of the most widely used antimicrobial agents, has been listed among the top 10 contaminants in US rivers. Environmental persistence, endocrine disruption effects, and antibiotic resistance induction capacity of TCS attract interests in its environmental fate and degradation. Herein, we found that TCS can be degraded by metal-reducing bacteria, Shewanella putrefaciens CN-32. The degradation was substantially facilitated by low-concentration organic matter (OM), which acted as an electron shuttle for extracellular electron transport, whereas TCS degradation was inhibited by further increased concentration of OM because of the sorption of triclosan by OM and thus its decreased microbial bioavailability. The novel dual role of ubiquitous OM in the reaction of TCS governs the environmental degradation and persistence of TCS. Our study highlights the unprecedented effects of OM on the reaction of emergent trace organic pollutants, with broader implications on their engineering treatment and environmental risk regulation.